1. Field of the Invention
The present invention relates to internal combustion engines and especially to improvements in internal combustion engines having an auxiliary ammonia gas feed metering gas through a dissociation system into the combustion chambers along with the normal hydrocarbon fuel-air mixture of the engine while leaning the engine below its normal operating fuel-air mixture.
2. Description of the Prior Art
In the past, a variety of internal combustion engines have been provided and typically these engines have a system for feeding a hydrocarbon fuel, such as gasoline mixed with air into the combustion chamber for running the engine. Such engines typically also have an electrical system which includes a generator or an alternator which may be connected through an electrical regulating circuit for charging a storage battery and for operating the electrical components of the engine of the vehicle. Internal combustion engines sometimes have hydrocarbon fuels mixed with air in a carburetor where the mixture is distributed into the combustion chambers of the engine. It is also typical to feed the air to the combustion chambers using a fuel injection system for injecting fuel directly into the combustion chambers. The present invention can be adapted to operate with either a carburetor or fuel injection system.
A variety of hydrogen fueled engines have been suggested in the past, including those using combinations of hydrogen and oxygen, which in some cases are generated in an electrolytic cell having an electrolyte including solutions of salts, acids or bases in water. The electrolytic cell breaks the water down between hydrogen and oxygen through electrolysis and the hydrogen or the hydrogen and oxygen in combination can then be used to run the engine. The advantage of the hydrogen and oxygen as fuel is that it is an efficient fuel which generates no pollution in that the combustion forms water in very minute quantities. Such engines, however, have not been brought into general use because of the inefficiency in the generation of hydrogen and oxygen through electrolysis which takes far more power than can be generated from the hydrogen and oxygen used as a fuel, even in high efficiency engines.
It has also been suggested to use small amounts of hydrogen added to the hydrocarbon fuel-air mixture to increase the efficiency or reduce the pollution of the internal combustion engine. One prior patent, U.S. Pat. No. 3,906,913, discusses in detail the advantages of the use of small amounts of hydrogen with the hydrocarbon fuel-air mixture of a vehicle and points out that the advantages of reduced pollution and increased mileage result from running the engine much leaner than can otherwise be accomplished because the misfire limit for hydrocarbon fuels can be well exceeded. The carbon monoxide and NO.sub.x (oxides of nitrogen) emissions have been found to decrease as the fuel-air ratio is made leaner and if the fuel-air ratio can be made sufficiently lean, it can be made substantially free of CO and NO.sub.x. This patent shows a hydrogen generator and means to control the feed of the hydrogen to the engine so that the conventionally fueled engine can be run very lean, well below where the engine would normally misfire as the engine approaches the flammability limit of the fuel. The normal flammability limit for hydrogen fuel-air mixtures occurs with a relatively high NO.sub.x formation rate and thereby imposes severe limitations on the lean limit operation for the fuel. Since hydrogen exhibits a flammability limit well below that of conventional hydrocarbon fuels, it is possible to reduce the NO.sub.x simply by using the hydrogen to change the fuel-air mixture to a much leaner mixture than would normally be allowed. The extension of the misfire limit to very lean equivalence ratios with hydrogen fuel also yields significant increases in the thermodynamic efficiency of the combustion process, thereby allowing a substantial increase in the mileage obtained on a conventional internal combustion fueled engine vehicle.
The difficulties in using hydrogen either as the sole fuel or in combination with a conventional internal combustion engine results from the hydrogen being a ubiquitous and very flammable gas, so that storage increases the hazards of operating the engine and in the general inefficiency in generating the hydrogen such as through electrolysis on the vehicle.
The present invention is directed toward the use of an ammonia gas used in combination with a conventional hydrocarbon fuel-air mixture to increase the efficiency of the engine and to reduce pollution in the engine. Ammonia has been mentioned as a constituent of various types of fuels in the past, both for internal combustion engines and for jet propulsion. One such fuel is a liquid mixture of ammonious nitrate in liquid ammonia which is a self-sustaining fuel combination requiring no addition of an oxident such as air. Ammonia is also used to manufacture hydrozene, a well known rocket fuel, and while ammonia does not support combustion, it will burn when mixed with oxygen in air to give a variety of products, principally nitrogen and water. Mixtures of nitrous oxide and ammonia in a rate of 3 to 2 will detonate with some violence yielding nitrogen and water.
One prior U.S. Patent showing the use of ammonia as constituent in fuel for internal combustion engines can be seen in the Drouilly U.S. Pat. No. 2,559,605, for a fuel mixture for internal combustion engines. In this patent, ammonia gas is fed from one storage cylinder into a pressure reducing chamber and a second bottle containing an auxiliary gas, such as ethanized illuminating gas, is fed into a second expansion chamber and the two gases are then fed into a mixing chamber, and from the mixing chamber into a carburetor. This patent also discusses the use of carbomonoxide, methyl ether, ethyl ether, methyl amine and ethyl amine in combination with ammonia. In the U.S. Pat. to Meyer, No. 1,671,158, a fuel for use in internal combustion engines consists of a mixture of hydrocarbon distillates with ether and a highly volatile basic material, which may be ammonia. The mixture can then be used in internal combustion engines according to the patent. The U.S. Pat. to Brooks, No. 1,748,507, shows a process of reducing stable hydrocarbon oils in which ammonia or certain alkaline compounds are mixed with light hydrocarbon oils to prevent discoloration and sedimentation. In two of these U.S. patents, ammonia is used in small amounts in a fuel mixture, which may then be used as a fuel in an internal combustion engine; while in the Drouilly patent, expanded ammonia gas is mixed with another gas to form a gaseous fuel mixture for running an internal combustion engine.
Other prior U.S. patents utilizing ammonia as a fuel include U.S. Pat. No. 3,150,645 which uses a method of operating a compression ignition engine using ammonia as the primary fuel; U.S. Pat. No. 1,384,946 for a composite motor fuel which uses reagents admixed with the fuel to neutralize or destroy the corrosive products of explosive combustion in the engine cylinders, which include among other reagents, ammonia. In U.S. Pat. No. 4,223,642, a small amount of ammonia gas is obtained from ammonia bicarbonate or ammonia carbonate for use in the internal combustion engine. In U.S. Pat. No. 2,140,254 to Zayka, an internal combustion engine is operated on ammonia as a fuel by dissociating a small portion of the ammonia into hydrogen and nitrogen, utilizing exhaust heat, and then adding the dissociated gas back into the ammonia gas to run the engine. The hydrogen apparently extends the flammability limits of the ammonia so that it can be used as a fuel. Ammonia, however, has only half the btu value per pound as gasoline, and therefore, by itself is not considered an efficient fuel. In addition, it's narrow flammability range makes it difficult to use as a fuel.
Other prior art patents can be seen in U.S. Pat. Nos. 4,036,180 and 4,230,072, both to Noguchi, et al., for fuel reforming systems for internal combustion engines reforming methanol; and in U.S. Pat. Nos. 1,899,869 for a gas engine; 4,054,423 for a variable pressure fuel generator and method; and in U.S. Pat. Nos. 3,915,125, 4,121,542 and 3,963,000.
The advantage in using ammonia in the present invention is that ammonia is useful as a convenient means for transporting small volumes of hydrogen since the gas obtained by decomposition contain 75% by volume of hydrogen and 25% by volume of nitrogen. The ammonia is easily liquefied either by cooling to below its normal boiling point of -33.42.degree. C. or by compression and can be stored in a liquid state in small compression cylinders. Ammonia can be thermally dissociated in the presence of certain catalysts to give nitrogen and hydrogen and dissociation can also be affected by photochemical means or by passing an electrical discharge through the gas. Ammonia can be obtained a number of ways, but is normally prepared synthetically by a modification of the Haber process using pressures between 200 and 1,000 atmospheres and temperatures between 400.degree. and 500.degree. C. along with a variety of catalysts. The present invention advantageously can be adapted as an add-on to existing hydrocarbon fueled internal combustion engines, as well as designed for new vehicles and allows a substantial increase in the mileage obtained from the hydrocarbon fuels and a reduction of at least certain pollutants in the exhaust of a vehicle and since the dissociated ammonia is metered in accordance with the requirements of the engine and the leaning of the engine can be similarly controlled, the efficiency can be easily optimized for any particular internal combustion engine.